Citing 36 deaths, the Food and Drug Administration chief warned consumers Tuesday not to use the herbal supplement kratom to ease opioid withdrawal and announce plans to step its regulatory oversight to combat the opioid epidemic.

The FDA public health advisory on kratom follows the Drug Enforcement Administration's reversal or at least delay of plans to classify kratom as a controlled substance on the same level as heroin and LSD.

FDA commissioner Scott Gottlieb says the FDA plans to work with the DEA to determine how kratom should be classified.

Kratom, a plant grown naturally in countries including Thailand and Malaysia, is widely sold in smoke shops and other locations as a powder that can be used in tea to slow the effects of opioid withdrawal. But it has addictive properties of its own, says a public health advisory related to the FDA's mounting concerns regarding risks associated with the use of kratom.

The FDA says kratom carries similar risks of abuse, addiction and in some cases, death, as opioids. It is also often used recreationally for its euphoric effects.

Along with opioid withdrawal, kratom is also believed to relieve fatigue, pain, cough and diarrhea. Anita Gupta, an osteopathic anesthesiologist and licensed pharmacist, has expressed concern about an increase in the use of kratom among her chronic pain patients.

Kratom users and advocates were "dismayed to learn of the DEA's plan to classify kratom as a Schedule 1 substance - the same classification as LSD and heroin - despite anecdotal and scientific evidence indicating kratom could be an effective opioid alternative," says Walter Prozialeck, chairman of the pharmacology department at Midwestern University Chicago College of Osteopathic Medicine.

Studies from Asia indicate kratom, in its pure form, has not been linked to any deaths in that part of the world, says Prozialieck. He blames a "lack of quality control in western countries including the U.S., which can lead to dangerous alterations of kratom or the addition of other drugs.

"The therapeutic potential of kratom is real, but more research is urgently needed to evaluate its safety and efficacy," he added. "One of my concerns is that a total ban will likely stifle such research."

Because kratom is unregulated, "you never know the real strength, ingredients, or how it's prepared," agrees Chris Barth, who used the medication Suboxone to recover from a pain pill addiction a decade ago.

"Limited access and or lack of knowledge of approved treatments is what's probably driving this." says Barth. "It's probably easier to 'do it yourself' with kratom ordered over the internet than find - if it's available - and pay for FDA approved, doctor supervised treatment."

Gottlieb also told his agency's criminal investigations staff that he may ask Congress for more authority and resources to fight the opioid epidemic, according to remarks prepared for delivery Tuesday afternoon.

Gottlieb also says in the remarks that a new working group with Customs and Border Patrol is working on stepped-up enforcement at entry points for illegal narcotics.

The fact Gottlieb is speaking to the investigations staff is significant because "if they find people here who are opening the gates to these drugs, there may be opportunities for the FDA to investigate at a high level," says Joshua Sharfstein, former principal deputy FDA commissioner in the Obama administration.

Importers, organized crime or others in the supply chain could be part of conspiracies to distribute illegal opioids, Sharfstein says.

FDA is already using import alerts and other authority to stop foreign, unapproved and misbranded drugs at the border to keep kratom shipments from entering the United States. Hundreds of shipments have already been detained and many are seized.

Still, more than 340 million packages reach the U.S. every year.

"Given that massive volume, it's estimated that only a small percentage of the illicit drugs smuggled through the international mail are being intercepted," Gottlieb said.

While it's very important to strengthen border enforcement, "the challenge is akin to pushing the tide back into the ocean," says Sharfstein.

Gottlieb, who did two previous stints at the FDA, has publicly expressed misgivings about how long it took the agency to truly address the crisis.

"We've learned a tragic lesson from the opioid crisis: that we must pay early attention to the potential for new products to cause addiction and we must take strong, decisive measures to intervene," said Gottlieb. "From the outset, the FDA must use its authority to protect the public from addictive substances like kratom, both as part of our commitment to stemming the opioid epidemic and preventing another from taking hold. "